Kentucky has a vast system of state highways: including interstates, parkways, U.S. routes, and state routes, Kentucky had 27441.407 miles of state maintained roads as of July 7, 2003. As of Dec. 1, 2003, official route logs listed 3716 individual numbered routes.

The majority of these routes are designated as state roads (as opposed to interstates, parkways, or U.S. routes). Among the transportation community, Kentucky is well known for designating some of the most seemingly undeserving routes as state roads. Kentucky’s state route system includes everything from superhighways such as KY 841 and KY 4 to residential streets in cities and one-lane roads twisting through the valleys and hills of Eastern Kentucky. Many of Kentucky’s minor state roads are “secret:” that is there are no signs indicating their state route number or that they are even state routes.

State and U.S. routes in Kentucky are classified as being either part of “state primary” system or “state secondary” system. These designations are also “secret” in that there is no difference in the style of signage used to mark the route.

Most of Kentucky’s state routes are assigned numbers in the 1 to 3999 range. In recent years, new state routes have usually been assigned numbers in 3000s; however, there has been some notable use of lower route numbers: the new industrial parkway in northeastern Kentucky was designated KY 67 and an old portion of KY 80 in the Jackson Purchase was recently redesignated KY 402.

Numbers in the 6000s are usually assigned to frontage roads and other supplemental routes. Though designated as Kentucky routes in route logs, signs for the 6000-series routes are rarely posted. (The only known signed 6000-series route is KY 6011 in Lyon County. See a photograph near the bottom of this page.)

The parkways are assigned state route numbers in the 9000s. These numbers are also unposted.

It is the usual policy that state route numbers not be duplicated among the various types of routes. For example, a state road should not use the same number as an interstate or a state road should not use the number as US route. However, there are two known exceptions to this rule. There is both a US 79 and KY 79 and an Interstate 471 and a KY 471. If I-66 or I-69 are constructed in Kentucky, KY 66 and KY 69 may be renumbered. Other routes have been renumbered because of new interstates in the past (see here).

Beginning April 1, 2009 the Louisville-Jefferson County metro government will take over maintenance of state roads and state controlled traffic signals in Jefferson County. The state will pay the metro government for the maintenance expenses.

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